Shock absorbing strut for airplanes



Oct, 20, 1942. E. w. CLEVELAND El'AL 2,299,613

SHOCK ABSORBING STRUT FOR AIRPLANES Filed Dec. 5, 1939 INVENTORS EPHEA/M w cLEVaA/Vo a E. PAHVO/VD MBA ER ATTORNEY Patented Oct. 20, 1942 Ephraim W.

Cleveland. Berea, Ohio, and a; Baymond Warner, Burbank, Calif,

orato The Cleveland Pneumatic Tool Company, Cleveland, Ohio, a corporation of Ohio Application December s, 1939, Serial No. 307,648 8 Claims. or. 244-104) This invention relates broadly to airplanes, but more particularly to shock absorbing struts for the nose or tail wheels airplanes.

One object of this invention is to produce-a shock strut including two telescoping cylinders capable of relative rotation, the upper cylinder being capable of attachment to the fuselage of the airplane, while the lower one carries the nose or tail wheel of the craft, thereby enabling free castoring action of the wheel when under load, that is, during landing or taxiing of the craft; the shock strut being equipped with self-centering means so that when the airplane reaches the ground, the nose or tail wheel will automatically be positioned in a fore to ait direction preparatory to the landing of the craft.

Another object of this invention, is to produce a nose or tail wheel support including an oleo shock strut enabling free castoring action of the wheel when in contact with the ground,'and' equipped with means for automatically causing 7 the wheel to assume the correct landing position when the airplane is air-borne or when the wheel is oil the ground.

Another object of this invention is to produce such shock struts in a manner forming a compact assembly which is strong, durable and emcient.

In the drawing:

Fig. l isa side elevational view, partly in section, of a shock absorbing strut embodying the invention.

Fig. 2 is an enlarged sectional view of the central portion or the strut shown in Fig. 1.

Fig. 3 is an enlarged sectional view of the lower portion of the strut shown in Fig. 1.

' Fig. 4 i: a cross sectional view taken in a plane indicated. by line H in Fig. 2.

Fig. 5 is a perspective view of one of the parts incorporated in the assembly.

Fig. 6 is a front elevational view of another strut also embodying the invention.

Referring to the drawing, the shock absorbing strut is shown to include two telescoping cylin- 4 ders In and H, the former being the outer cylinder closed at its upper end by a head I! through which the shock absorber may be attached to the fuselage of the airplane. The inner cylinder H is of a diameter materially smaller than that of the outer cylinder III, thereby forming between the two cylinders an annular chamber or compartment l3 closed at its lower end by a bushing it formed at its lower end with an annular flange l5 resting against the bottom of a counterbore It provided in the lower or inner end of the outer cylinder II; The bushing ll flts closely portion of the cylinder between the 'two cylinders to act as a sliding bearing therebetween, and in practice is preferably made of good bearing material such as bronze or the like. In the present construction,

the bushing I4 is rigidly secured to the outer cylinder II, by any suitable means such as'cap screws ll operatively carried by the cylinder I0.

and projecting part way into complementary radial bores I! provided within the annular flange l5. Below the bushing 14, there is provided in the counterbore it suitable packing rings it! held in operative position by a gland nut 20, thereby assuring a fluid tight joint between the two cyl- 'inders. The upper end of the compartment i3 is closed by a sleeve-like head it screwed on the inner end of the inner cylinder II and secured thereon against accidental relative rotation by radial pipe plugs 22 screwed in the head 21 and cylinder II. The head 2| also fits closely in the cylinder"! to act, like the bushing H, as a sliding bearing between the two cylinders. In the present construction, the lower end face of the head 2|, hereinafter referred to as the outer end of the head, is especially machined to produce a helical cylinder cam 23 corresponding to and capable of engagement with a similar cam 24 formed on the upper end face, hereinafter referred to as the inner end, of the bushing M, the purpose of which will be explained later.

In the construction shown, there is also included in the outer cylinder Ill a'metering housing or tube 25 depending from the upper end l0 into the cylinder H, and terminated by a partition or diaphragm 26 having a central orifice 21 extending therethrough. q p

. Intermediate its ends, the cylinder H is proyided with a cross wall 28 carrying a metering pin 2'! extending upwardly therefrom through the oriflce 21 for varying the fluid conveying capacity thereof.

In the construction shown in Fig. l, the lower or outer end of the inner cylinder III is formed with an integral laterally extending boss 30 having a bore- 3! extending longitudinally therethrough and substantially parallel to the common center axis of the cylinders l0 and H. In this bore is rotatably mounted a spindle 32 formed integrally with a wheel knuckle 33 which depends from the spindle 32 in angular relation therewith. In practice the knuckle 33 is preferably made like afork and carries a wheel rotatable on a cross shaft 35 carried by the free end of the knuckle 33. The spindle 32 is-preierably journal'ed within roller bearings 36 and 31 adequately mounted within the bore-3| oi the boss tawmcn hose is 7 air admitted shock absorber, the liquid airplane.

strut being well known in the art, iurther exclosed at the upper end by a cover 33 and at its lower end by a washer 39. In the present construction, there is also screwed in the bore 8i above the roller bearing 31 a as held therein by at least one cup screw M.

Above the ring did, there is a similar ring 52 which is locked to the spindle 32 against rotation relative thereto by two keys d3 enabling limited axle movement of the ring 42 relative to the spindle 82. The abutting end faces 01 the rings to oi oi are-shaped to form helical cams M and 65 respectively, which cams are constantly urged toward each other by a compression spring it acting on the ring 522.

Extending through the wall of the cylinder it near the head ii, there is one or more ports di afiording communication between the cylinder id and the compartment It, while the tube 25 near the upper end thereof is provided with similar ports 4'8. Near its outer end, the cylinder to is provided with a radially extending threaded bore it adapted to receive a filler plug 49 and air valve 50. The interior of the tube 25 together with the interior of the cylinder it above the head it, forms a chamber and the interior of the cylinder i i a chamber52, which chambers 55 and 52 are separated by the partition 28.

In the construction shown in Mg. 6, the cylinder ii instead of being formed with the boss 3d housing the spindle it? as shown in Fig. l, has its outer end carrying an ofiset wheel knuckle [:33 rigidly secured thereon by a cross bolt 561. The knuckle 53 operatively carries a wheel 36' corresponding to the wheel 34 in Fig. 1. Internally, the construction is the exact replica of that shown in Figs. 1 and 2, the outer cylinder iii. being intei'changeable with the corresponding cylinder 0. a

Before installation, the shock absorber is first fully extended and while in that position liquid such as oil is poured into the cylinders through the bore 48 by removing the. plug 49. When the, level-of the liquid finally reaches the bore 68, the

shock absorber is slowly compressed into complete contracted position, thereby causing the oil to entirely fill the compartment i3 through the port 41, while the excessive amount of liquid will escape through the bore 48. Thereafter the plug 29 is again screwed into position and compressed into the cylinder 25 through the air valve 50, causing a partial extension of the shock absorber while under static load.

- planation of the same is not thought necessary.

Referring now more particularly to the invention, when the landing wheel 34 is in contact with the ground andv the shock absorber is in-a more I or less compressed condition, the head 2| of the cylinder ii is spaced axially from the bushing M, thereby enabling free relative rotation of the two cylinders 60 and H, and the consequential castoring action of the wheel 34 about the center axis of the shock absorber. In the construction shown in Fig. l, the spindle 32 being relatively In the operation, during landing and taxiing operations resulting in the compression of the from the chamber 52 ,will flow through the orifice 21 into the chamber 5|, and therefrom. into the compartment it through the port 41. In this instance. the metering pin 29 slidable throughthe orifice Zlwill gradually reduce the fluid conveying capacity of the orifice and gradually check the compression of the strut, thereby resulting in a resistance to the compression of the strut additional to that resulting from the compressed air stored within the upper end of the chamber 5|.

The extension of the strut resulting from the subsequent recoil movement of the airplane relative to the wheel 34, will be checked by the displacement ,01' the liquid from the compartment l3 through the rather small port 41, and from the cylinder l0 into the tube 25 through the ports 41', thereby producing an efilcient means forcushioning the landing and taxiing shocks of the The shock absorbing functions of the free to rotate within the bore 3! of the boss 30 will cooperate withthe relative rotation of the two cylinders to prevent lateral rapid oscillation 'or shimmy of the wheel, a feature forming the basis of our co-pending application, Serial 1N0. 199,284. As the spindle 32 rotates within the bore ii, the ring 62, due to the. engagement of its cam it with the similar cam 44 of the ring 40, will move axially relative to the spindle 32 by compressing the spring it, I

When the craft leaves the ground or is airborne, the weight of the wheel together with the action of the compressed air within the upper end of the chamber 5i will cause the complete extension of the strut, which extension is ultimately limited by the head 2! resting on the bushing iii. Toward the end of 'the extension stroke of the strut, the cam 23 will engage the cam 2d and cause axial rotation of the cylinder M resulting in the boss 30 to be positioned as shown in Fig. 1, that is, in adequate position to enable trailing condition of the wheel 34 relative to the spindle 32 within a vertical plane parallel to the vertical planes within which are located the main landing wheels of the airplane. In this 45, effect the rotation of the spindle 32 resulting in the location of the wheels 34 within the vertical plane above referred to, or in other words, resulting in the rotation of the wheel 34 into a fore to aft or, landing position.

In the construction shown in Fig. 6, upon engagement of the cams 23 and 24, the inner cylinder M will be rotated into a predetermined position relative to the cylinder III, which position is calculated to result in the wheel 34 assuming a fore to aft alignment or landing position.

Although the foregoing description is necessarily of a detailed character, in order to completely set forth the invention, it is to be understood that the specific terminology is not intended tobe restrictive or confining and it is to be further understood that various rearrangements of parts and modifications of structural detail may be resorted to without departing from the scope or spirit of the invention as herein claimed. a

for maintaining them in coaxial alignment, and

cam means on said bearings capable of interengagement near the end of the'extension stroke of the strut for relatively'rotating said cylinders '70 to a specific alignment about a common axis and immediately thereafter for-limiting said exten sion stroke.

It relative rotation,

2. A shock absorbing strut for aircraft .com-

telescoping cylinders capableof a sliding bearing fixed to the prisinga pair of inner end of each cylinder, and a helical cam on each of said bearings adapted to engage each other at a point near the end of the extension stroke of said cylinders to rotate said cylinders to a predetermined aligned position as the extension stroke continues.

3. A shock absorbing strut for aircraft comprising a pair of telescoping cylinders capable of relative rotation, a pair of sliding bearings between said cylinders one fixed to the outer and the other to the inner cylinder, and a helical cam on each of said bearings adapted to engage each other at a point near the end of the extension stroke of said cylinders to rotate one of said cylinders relative to the other into a predetermined aligned position as the extensionstroke continues.

4. A shock absorbing strut for aircraft comprising a pair of telescoping cylinders capable of relative rotation, a pair of bushings between said cylinders one carried by the outer and the other by the inner cylinder, radially extending locking means through each bushingand its carrying cylinder preventing relative rotation therebetween, and cam means on each bushing adapted to engage each other at a point near the end of the extension stroke of said cylinders to rotatably align said cylinders into a predetermined position as the extension stroke continues.

5. A landing gear for aircraft comprising, the combination of a cylinder, a piston slidably and rotatably mounted within the cylinder, a wheel supported on the lower extremity of said piston, a cam follower rigidly mounted on the upper extremity of said piston, said cam follower being provided with a downwardly depending portion having a curved surface, a cam within the cylinder, said cam being rigidly attached to the cylinder at a point below the cam follower and being provided with, an upstanding member having a surface which is curved in a manner similar to that of the cam follower, and means to force the piston downward in the cylinder so that the two surfaces will engage each other, thereby causing a partial rotation of the piston and the wheel to which it is attached.

6.'A shock absorbing strut for aircraft comprising a pair of telscoping cylinders capable of 'relative rotation, a pair of sliding bearings between said cylinders one fixed to the outer and the other to the inner cylinder, and a cam on each of said bearings adapted to engage each other at a point near the end of the extension stroke of said cylinders to rotate one of said cylinders relative to the other into a predetermined aligned position as the extension stroke continues.

I. A'landing gear for aircraft comprising, the combination of a cylinder, a piston slidably and rotatably mounted within the cylinder, a wheel mounted on the lower extremity of said piston, a cam follower provided with a curved surface rigidly mounted on the upper extremity of said piston, a cam having a similarly constructed surface rigidly attached to said cylinder at a point below thecam follower, and means to force the piston downward in the cylinder so that the two above mentioned surfaces will engage each other, thereby causing a partial rotation of the piston and the wheel to which it is attached.

8. A shock absorbing strut for aircraft comprising a pair of telescoping cylinders capable of relative rotation, a pair of relatively shorttubular members between said cylinders one fixed to the outer and the other to the inner cylinder,

'and a cam on each of said members adapted to engage each other at a point near the end of the extension stroke of said cylinders to rotate one of said cylinders relative to the other into a predetermined aligned position as the extension stroke continues. i EPHRAIM W; CLEVELAND.

E. RAYMOND WARNER. 

